While you're doing all the tests etc keep the binding as is. When you want to do final assembly, the simplest thing, is to do it with the cells sitting around 3.2V (nominal voltage)as that's the midground. I like to set cells in 4-cell blocks because if ever I need to take it apart, don't want to undo & redo everything, so each "block" also get's a Pull String. People thought that was nuts, until they had to pull some cells from a large pack... Saved me a lot of stressed when doing reconfigs & tests but that's just me.... I don't like extra work when it's just not nescessary.
Everyone freaking over swelling.... LFP expands & contracts when in a Prismatic format like these, usually no more than 1.5mm sideways @ nominal temps (25C/72F). Temps DO affect the amount of expansion/contraction. this is expected as well (even in many of the docs too). The Higher the Amperage Pushed or Pulled also affects the rate of expansion (due to heat generated by the process). IF you charge at 0.5C you will see more expansion than if charging at 0.25C. (Charging is the Usual Cause for the swelling process).
There are a lot of ways to bind cells, one of the best is the Nylon Pallet Straps (without buckle) so if you have a buddy that works in a warehouse maybe you can borrow a binder & but the strapping. Alternately, Packing Fibretape also works quite well (1" wide ok, 1.5" better). I clamp the "blocks of cells" lightly with Quick-Grip Clamps with wood to spread the pressure evenly (very light hand squeeze tight) and then bind around the upper & bottom, then remove the clamp and another around the middle. This hasn't failed me yet. DO NOTE, that I built my battery boxes with 3/4" Ply to a tight spec, so the cells are "snug" within anyways. and I mean "snug" as in, takes two people to pull a bundle out because someone has to hold the box down, "snug" (ok borderline Tight LOL). Lesson Learned, DISCHARGE the cells BEFORE pulling them out !